Hi Stan
for HO you might be able you get away with The Bachmann On30 ones IF you are working with a mineral/ore that is of a lower density like gypsum or similar. You need a big wagon to haul the maximum weight the track will stand as opposed to something like lead ore that is very heavy and a small wagon will get you very close the maximum axle loads a small mining line could handle without causing derailments with rail spreading or bending rails at joints etc

Moral of story: If you have the cars available, choose your industry to suit